Free fatty acids, complement activation, and polyclonal B-cell stimulation as factors in the immunopathogenesis of African trypanosomiasis

Human and animal forms of African trypanosomiasis are characterised by sustained hypocomplementaemia, gross hypergammaglobulinaemia M, and profound immunosuppression. It is suggested that this hypocomplementaemia is probably due to the action of a trypanosome-derived complement-activating factor and that the elevated IgM levels may be the combined result of this decomplementation, together with a subsequent failure of the normal IgM-to-IgG antibody switch mechanism and polyclonal B-lymphocyte activation by a trypanosome-generated mitogen. The immunosuppression in this disease may be a result of the collective immunosuppressive effects of trypanosome-derived immune-modulating free fatty acids, polyclonally stimulating B-cell mitogen, and complement-activating factors.

IgM and antibody measurement in the diagnosis and management of Gambian trypanosomiasis

Serum and cerebrospinal fluid (CSF) IgM were measured in 182 patients at various stages of Gambian sleeping sickness and correlated with antibody levels measured by enzyme-linked immunosorbent assay (ELISA). Each of these tests in serum gave a 30% false negative result, but when both were used this fell to 12%. Measurements of IgM in CSF were raised in 87% of patients with advanced disease and in none of the early cases. The IgM levels fell slowly to normal by 12 months after treatment. A high level at this time, or a rise after treatment, was helpful in diagnosing relapsed patients. Antibody levels in CSF were of no use in diagnosis or prognosis, and were raised in many controls.

[Comparative value of immunofluorescence and immunoenzymology on figured antigen in the immunological diagnosis of African trypanosomiasis]

Indirect immunoperoxydase method is compared with indirect immunofluorescence using immunized animal and human sera, and negative control sera. The obtained results show a good statisticly established concord and allow to propose the indirect immunoperoxydase method being used in the biological diagnostic of african Trypanosomiasis because its easy carrying out and its examin with an ordinary microscope.

[Indirect immunofluorescence study of 200 cases of tryponosomiasis due to Trypanosoma gambiense]

The sera and CSF collected on 200 patients suffering from sleeping sickness were collected before treatment and tested with fluorescent antibody test. The proportion of strongly positive sera is very important in the first period and decreases progressively with the alteration of CSF. This shows the reliability of the FAT technique as a screening method because it is in the first period that it is difficult to diagnose the disease. 14% of CSF collected during the 1st period are positive with FAT: this fluorescence certainly reflects the presence of the parasite and confirms Burke et al. observations. The notion of periodicity can be questioned as well as the treatment protocol whick is traditionally based on the CSF cytochemistry.

Immunodepression during Trypanosoma brucei gambiense infections in the field vole, Microtus montanus

The effects of Trypanosoma brucei gambiense infections upon immune responses were examined in an outbred laboratory colony of field voles. Microtus montanus. Antibody levels to challenge with heterologous erythrocytes and bovine serum albumin were significantly depressed in infected animals. Trypanosome infections impaired both primary and secondary humoral responses, although previously established specific antibody levels were not affected by infection. Specific antibody-producing capabilities of previously infected, trypanoicidal drug-treated voles were found to be comparable to uninfected controls, within 3 days following chemotherapy. Cell-mediated hypersensitivity responses to oxazolone were also significantly depressed by trypanosome infection; responses to the initial sensitization of oxazolone and to secondary challenge treatments were depressed compared to uninfected controls. Possible mechanisms of trypanosome-induced immunodepression are discussed.

Effects of Trypanosoma brucei gambiense infections in Microtus montanus on susceptibility to Ehrlich's tumors

Trypanosoma brucei gambiense infections in the field vole Microtus montanus increased susceptibility to Ehrlich's tumor growth. Whereas uninfected voles were totally resistant to intraperitoneal Ehrlich's ascites tumor cell challenge, over 78% of the animals infected with the trypanosomes developed tumors after challenge. Likewise, when Ehrlich's ascites cells were injected subcutaneously to induce solid tumor formation, only 7% of uninfected controls developed tumors, whereas over 82% of trypanosome-infected animals exhibited malignancies after Ehrlich's cell challenge. Finally, when solid tumors grown in albino CD-1 mice were implanted subcutaneously into uninfected voles, the tumor mass rapidly diminished in size and could not be found when animals were examined 2 weeks postimplant. However, in trypanosome-infected voles, implanted tumors exhibited pronounced expansion, and viable, solid tumors were recovered from over 70% of the challenged voles at 2 weeks postimplant. The implications of trypanosome-induced immunosuppression, especially toward susceptibility to neoplastic growth, are discussed.

[Electrosyneresis in the diagnosis of African trypanosomiasis]

Comparative studies were carried out on serums from rabbits inoculated with several Trypanosoma strains and 50 serums from sleeping sickness cases. The techniques used were antigen-antibody reaction in gel according to Ouchterlony, and electrosynerese for which directions are outlined. Electrosynerese has been shown to be a much faster and more sensitive method of detecting precipitating antibodies in trypanosomiasis.

["Trypanosoma brucei gambiense", antigenic study. III. Hemagglutination reaction with specific antigenic fractions]

The tannic acid hemagglutination method was applied to experimentally infected rodents sera. The antigens were Trypanosoma gambiense fractions separated by gel filtration on Sephadex G 200. Two fractions, at least, showed specific activity.

[Preparation of a standardized antigenic extract from several strains of African trypansomes]

The preparation of a soluble antigen from african trypanosomes is described below. It is important to observe the following steps: --minimal dose of the phytohemagglutinin must be placed in rapid contact with the trypanosomes; --the standard speed of the different centrifugations must be strictly observed; --a thorough washing of the trypanosomes must be carried out to eliminate the hetero-antigens, but caution should be excercised, as over washing is harmful to the Trypanosomes.

[Comparative immunoelectrophoretic analysis of culture and bloodstream forms of "trypanosoma" (Trypanozoon) brucei gambiense". Demonstration of stage and antigenic type specific antigens (author's transl)]

The comparative immunoelectrophoretic analysis of the antigenic structures of culture and bloodstream forms with cross absorption tests confirm the existence among Trypanosoma gambiense antigens of: --numerous antigenic components common to culture and bloodstream forms;--several antigenic components specific of either culture forms or bloodstream forms. Among the latter, two components are shown to be specific of the antigenic type and appear to support the immunochemical specificity of each variant.

A pattern in the development of agglutinogenic antigens of cyclically transmitted isolates of Trypanosoma gambiense

Three isolates of T. gambiense, belonging to 2 serologically different substrains of the species, were cyclically transmitted to rabbits and monkeys by G. morsitans or G. tachinoides. Sera collected from the infected animals were tested for agglutinating antibodies to 17 different serotype antigens prepared from rodent-adapted isolates of T. gambiense. The first antibodies detected in sera from all of the animals agglutinated the same serotype antigen L2, indicating that it possibly consisted of trypanosomes bearing a basic antigen of T. gambiense. In 2 animals infected with 1 isolate the development of antibody to the common serotype L2 was accompanied by the development of antibody to a second serotype U1. Comparisons of the patterns in which antibodies were produced to other serotype antigens in different animals indicated that there were many similarities in the sequences in which they developed in different rabbits infected with (a) any 1 isolate (b) 2 different isolates of 1 substrain and (c) isolates of 2 serologically different substrains. There were also similarities in the sequences in which the antigens developed in rabbits and monkeys infected with an isolate by the same fly or by different tsetse flies. The ordered sequence in which these 3 cyclically transmitted isolates of T. gambiense, of significantly varied origin and laboratory history, produced variant antigens in hosts of different species provides further evidence to support previous suggestions that antigenic variation in trypanosomes is an adaptive process, rather than one involving selection of mutants.